Pressure releasable locking mechanism for fluid pressure pistons



Sept. 9, 1952 H. E. ROSE 2,609,793

PRESSURE RELEASABLE LOCKING MECHANISM FOR FLUID PRES-SURE PISTONS Original Filed Nov. 30, 1942 2 SHEETSSl-IEET 1 HOWARD E. Ross,

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av @JMAW bept'. 9, 1952 H. E. ROSE 2,609,793

PRESSURE RELEASABLE LOCKING MECHANISM FOR FLUID PRESSURE PISTONS Original Filed Nov. 30, 1942 2 SHEETS-SHEET 2 94 86 f g 90 9g 56 j 40 9/ 49 58 57 67 w a; 63 ,3 34 a/ 59 54 44 J 76 475 V J k F 70 M A r g \u 73 52 7/ 72 77 43 96 J 76 j j 53 a? /A i EA/ IE: 9392 E55 89 J/owneo E. 2255) 0/ 5) Q patented Sept. 9, 1952 PRESSURE RELEASABLEJ LOCKINGMECI-IA- NISM FOR, FLUID PRESSURE PISTONS Howard'iE. Rose, Brecksville, Ohio, ]as'sig'nor, l)y' .gmesne assignments, to Alco'ValveCon'St. Louis, I l

Mo., a corporation of Missouri Original application November 30, 1942, Serial T V No. 467,359. Divided and this application Jan nary 12, 1948, Serial No. 1,773

' The present inventionrelates to a pressure releasable'locking mechanism for a fluid pressure piston. It also includes apparatus for exhausting pressure fluids that have bled around the pies'sure operated parts of mechanisms to the actuated parts of'the mechanisms themselves.

"It-is an object of the invention to provide a mechanical locking mechanism that will secure a" pressure operated piston in a chosen position along lts' lengthof travel, which look has pressure operated means for effecting its release.

"jAiu'rther object of the invention is to provide 'aiocking means of this kind which comprises a mechanical locking element that normally tends to lock the fpistonin oneof its positions, but which is automatically withdrawn when the fluid pressure "for operating the piston is applied thereto. p It is a specific object of th'einvention to provide sucha locking means having a plurality of locking positions, andespecially to provide such a 'locking'means which may operate with a reverseacting piston that is subje'ctedalternately to flnidpressure onits oppositeends.

Other objects include the provision of a looking, mechanism for a fluid pressure operated windshield wiperwhich can hold the windshield wiper in on'e of its positions, and particularly in one of"itsextremepositions; and to provide such a 'ltick'ior a w'indshield wiper that may selectively hold the'windshield wiper-ineither of two excreme passions. Other obj'ectswill appear from the description torcnow.

In this application, reference is made to a piston and to a'cylinder. It will be understood that these' ter'ms are used in a general sense unless otherwise" specified and; are designed to include varioustypes of fluid chambers, usually generically called cylinders, in which movable members, usually generically called pistons, are "operated back and-forth by pressure differentials obtained 'on' oppos'itesides of the mavens members.

Fig. 3 is a"transverse stion through one of 9 Claims. (Cl. 121-40) the;fwint'lshield'wiper units, taken on the line 3-3 of Fig. l;

Fig. 4 is an elevation ofone of the windshield wiper units, taken on the line 4-4 of Fig. 1;

Fig. 5 is a longitudinal section through one of the windshield wiper units, taken on the line 5--5 of Fig. 2, showing the piston in one extreme position;

Fig. 6 is a view similar to Fig. 5, but showing the piston iiran intermediate position, and

' Fig. 7 is a vertical section on the line Tl-! in Fig. 5.

In general, the mechanism comprises oneor more fluid motors, here shown as windshield wiper units, two being'here shown at 30 and3l. The mechanism also includes a control valve 32. A line '33 is connected to a hydraulic pressure line through an adjustable cutoff or speed control valve 34. A return line 35 is likewise connected to thehydr'aulic system. This return line runs to a'T35 from which one branch 31 is connected into the control valve 32, and the other branch 38 extends to another T39, from which the branches and 4| are connected into the windshield units 30 and 3 I, respectively.

Two lines 42 and 43 lead from the control valve 32 to the wiper units 30 and 3!, respectively. The two line 42and 43 are alternatively pressure and exhaust lines. The two units 30 and 3 I are connected'bya line 44. T

The windshield units are identical, and Figs. 2 to 5 may be either one of them. For convenience in the following description, it will be assumed that Fig.- 5 represents the wiper unit 30.. This unit-includes a'housing 48 through which extends acylinder 49. A head5ll is attached to one end and a head 5l to the other end. The head50 reoeives 'the line 43 and the head 5| receives the line 44, so that the two lines43- and 44 are put into communication with opposite ends of the cylinder. The cylinder head 50 has areduce'd circular? cutout 52 in it and a similar cutout 53 is found inthe head 5| A small port- 54 in the cylinder head 50 terminates ina valve 'seat 55 that receives a ball valve 56. This ball valve constitutes acheckvalve, as will appear. In the head 5|, there are a similar port5l, a-seat 5 8, anda ball valve 59. V y

Reciprocable within the cylinder 49 is a piston 60. This piston has a rack 6| on itsupper'surface thatengages with a gear 62 mounted ona shaft 63' to drive the windshieldwiper W back and forth.

The piston is symmetrical about its center transverse section. At one end, it is cut away to These plugs are ported at 12 and 13, respectively. V The piston opening at its middle portion has a reduced portion 14 to receive a slide valve '15.

side in Fig. it has two opposite flats I6 extending more than half the distance across the re- 110. The valve 15 is not ported, but from its left-hand duced part 14 of the piston. At right angles to the flats 16 are similar flats 11 extending the right-hand end of the piston.

Springs 8!] and 8| act against 18 and Ti. At their inner ends, these springs bear against spiders 83 and 84 engaging against the ends of the reduced portions 14. These spiders admit oil freely past them and into the flats 16 and TI. The spiders 83 and 84 are en'gageable against shoulders in the piston and thus locate the valve in a central position.

The piston 60 is provided with a relief groove 86, into which are disposed two notches B1 and 88 on'its lower side. These are adapted to be engaged by a cup-like plunger 89, and, as will appear, will retain the wipers in their rest positions. The plunger 89 i urged into engaging position by a spring 99 abutting against a fitting 9! that receives the exhaust line dill The piston 89 operates within a cylindrical opening 92 in the housing 48. i

The upper portion'of the cylinder 92 is connected with two passages 93 and SM. Theipa'ssage 93 leads to aball-type check valve 95,.fro'm which" a port 96 extends for communication with the left end of the main cylinder 49 of themechan'ism. This'c'ommunication is limited tosuch times as a notch 97 in the piston 68 registers with the arrot. Similarly, the port, 94 communicates with the ball-type check valve'93 opening into a port 99 that may register with a notch Hill in the other end of the piston. Z

Operation The operation will be described in connection withhydraulically operated windshield wipers, as the mechanism is especially valuable therein. However, it is usable elsewhere than in windshield wipers, and by fluid other. than liquid. Also, the pressure differentials may be obtained by pressure reduction below a normal fixed'pressure, rather than by pressure increase above the same, as illustrated'by the difference between hydraulically operated windshield wipers and those operated from engine, intakemanifold vacuum.

During operation, when hydraulic fluid is admitted through .the'line -44, it creates a pressure against the right-hand end of the piston-displacing the piston until it is stopped eitherat the end of its normalstrokeor prior thereto. After such stopping of the piston, the pressure builds up against the right-hand end of the .valve iii and displaces it or not, depending upon the other wipers position. As the pressure builds up through the notch Hit, it flows past theball-type check valve and maintains the locking piston 89 down'a'gainst the spring 90] Upon a subsequent reversal of the oil pressures, the check valve 98 retains the pressure upon the piston89 until the high pressure is subsequently introduced through the line 43 and the notch 91 to act upon the piston back in the same manner. a

from

4 The pressure oil flowing into the right end of the cylinder 49 acts against the piston 65), and applies pressure to the right end of the valve 15. The resistance of the springs 89 and 81 is greater than the normal resistance or the wipers and the mechanism] in regular ope soon; f- For instance, the valve 75 may have a resistance of 250 p. s. i., which is greater than the normal operat ing resistance of the movable parts of the wiper. Hence, the entire, piston 50 usually moves to the left to theend of its stroke, without alteration of the position of the valve i5 in the piston. When thepiston'is stopped, the resistance goes quickly 'beyondthe-250 p. s. i., and the valve 15 is forced to the left, permitting oil to flow through the piston, into the line 4 3 and against the piston 0f the other wiper unit, moving it to the left,

until it has reached its other position.

Atthis point, the pressure again rises. It must be above 250 p. s. i. to have held the valve 75 open. When the piston of the second unit stops, the pressure begins to act upon its valve 15against its additional resistance of 250 p. s. i."

The reversing valve mechanism 32 is described in detail in the parent case referred to, and here it need only be mentioned that it is designed always to reverse the high pressure and low pressure connections when the pressure in the eiiisting high pressure line attains 'avalue'g'reater than that of one valve l5, but'less than that of all of the valves '55 inserie's. Where the springs and Si load the valves '55 to 250 p. s. i. each, a reversing valve pressure-of 400 p. s. i. is, typical.

When the control valve reverses, the line 43 becomes an exhaust line, and pressurefislapplied to the line 42 to move the wipers back] At'such time, the oil between the pistons, including that in the line 24, will remain practically undirnin ished. Therefore, both wipers move back 'insy'n chronism. At the end of this reverse stroke, both valves 15 are urged open simultaneously, offering their combined resistance of 500 s. s. i., and the control valve will again reverse.

During continued operation,.the two valves l5 may open only as necessary to'keep theoil supply between the pistons full. I f

' The foregoing values are only typical. The critical factors are to have the combined ordinary operating resistances of the wipersf plus that of all of the valves 75 except one, less than the resistance of the reversing valve, but to have the combined resistance of all the valves, 15 greater than that of the reversing valve. Pressures in valves obviously means pressure differentials between the high pressureand low pressure sides. 7

It will be observed byreferring.to Figficthata dashpot action is provided ateach end of'the stroke of each piston. For example... as the piston 69 moves to the left in Fig. 5,, at the end of its stroke, the projection 61 will-begin its loose engagement in .the smaller cylindricalportion 52 This means that a quantity of oil is retainedbetween the cylinder head and the piston head, which is checked by the seating of the ba1l56. This trapped oil can escape only around the loose fit of the portion 6! in the portion 52. Thus, a dashpot action is provided. This, of-course, is relieved to permit the piston to move away from the cylinder head by the moving of ,thecheck ball BBiromitsseat. l' I As hasbeen noted, the plunger 89 is adapted to lock the pistons in either of their extreme positions. If the pistons are'locked at the start of any cycle of operatiomone. of the slots 9.'l ;or

5. till) willbe. in registry with eitherportfifi ores, respectively.

, Assume the pistons are at. theright as shown in Fig. 5. If, upon restart'by opening of the valve 34, pressure returns through the, lines}, it flows throughthe port 96 to depress the. plunger 89 Italsd-displaces the valve 15, flows through the line 44, and acts to depress thelocking plunger in the piston of the other wiper un it. After this has occurred, itsiurther eifort to displace the other valve '15 results in, reversal of thefcontrbl valve, attended by a lowering of the pressureon the'leftsi'de of the pistons. But the check valves 95 retain the previously introduced high pressure oil againstthe plunger!!!) so that it is held down. The supply of oil at high pressure for suchpur pose isfrenewed atthe end of each stroke.

If the start occurs with the pressure introduced atthe end ofthe cylinders where the pistonsf'are then located, as at thelrightjendsofthe pistons in Fig. .5, oil under pressure moves orjtend's to move the valve orthe rightward one of thepis jtonsand thereby appliespressureto the oilto the left' of Such, piston. This. latter pressure, causes oil; to flow back through itsball check valve .95 I to release its locking plunger, prior to causingithe' control valve 32 to reverse. Upon reversal of. "the control valve, and consequent reduction o f the pressures aforesaid, the cheok valve 95, retains the high,.'unlocking pressure against thelocking plunger 89. ofthe rightward piston. When pressure reversal is completed, high pressure is introduoed to the left end of the other piston, and

acts past its check valve 95 tounlock its locking the wipers will start.

plunger 89. Finally, on an additional reversal,

{It is readily apparenthow unlocking willoccur.

ifionly one wiper is looked 3 1 .Therelief groove 86 extends around the piston. Itis-always in communication with one or t he ball valves, and thereby readily releases any pressure that might build up around the wiper shaft, as these valves have relatively light resistance. The disposition of the detent notches 8'! and 88 in this groove prevents scraping of the cylinder by any burrs on their edges that might be turned up by the detent plunger.

When the main speed control valve 34 is closed, the pressure acting against the piston 89 gradually bleeds around the upper part of the piston and through the opening in the top thereof to relieve itself through the line 49. Also, pressure on one or the other sides of the piston 60 gradually relieves itself aroundthe piston and into the tube 40. 7 When the piston 89 is relieved, it is moved by its spring 90 into one of thenotches 81 or 8B and locks the wiperin position until the operation is started again. This is a mechanical look. It will be observed that this mechanical .1001: can be relieved whenever pressure is built up enough through one of the notches 91 or I06 to force back the locking piston.

An adjustment of the cutoiT valve 34 alters the speed with which the various pressures can be built up, and, therefore, it varies the speed of operation of the entire mechanism.

If one of the wipers is blocked, as by slush or ice, the other operates through its complete cycle and the blocked one operates through the sweep permitted by the obstruction. If both are blocked, they sweep through the stroke per 'mitted. This comes about because a blocking of one wiper unit limits the movement of its piston with the same effect on the pressures as if the piston had reached the end of its stroke. In subthe, obstruction with 1 some force a If thefwipers" become desynchroniz ed, they will alvva from either directionuntilall have been stopped.

.Ifbne of the wipers 'becfomes'permanently blocked in a ,fixed position, the other wiperwill continue to operate through its. full permitted stroke. Also,fboth wipers may operate on a limited stroke or one in a stalled, and the other on alimited stroke. In every case, resynchronization is automatic. The number of wiper unitsused can bemul tiplied indefinitely. It is necessary only to have the total resistances of all of the valve lSin series greater than the neutralizing force on'the reversing valve, but withianyless than the total number less than the neutralizing force onthe reversing'valve, Q flhe' frneehanisin canbe used ,with one Wiper, as the unit 39, in which case, when the pistonlill would stop, the control valvewould shift. ,Ad vantages of Ioperatin ga'single wiper thisway are thatitfwouldrnot-requii'e a full stroketo reverse itself, and'that it wouldhave the beating action tending tofb'reak downany obstructions to itscyclingforitsfullsWeepQ ,Whatis claimedis: I I

1. In. combination, cylinder, a piston lke member movable oppositely therein, a rece'ssin the member, alocking element rriovably mounted on the cylinder for engagement. withftheieoess to lock the piston member and cylinder to-,

, gather, and for withdrawal from lockin'gyp' siwall to move it and Withdraw the locking velement from the piston member, check valveineans to prevent back-flow of fluid under pressure; in the passage means, means providing predetermined escape; for the pressure from the movable wa1l,.an'd springing means acting to urge. the locking element into locking position, v

2; In combination, a cylinder, aJpiston-like member movable oppositelytherein, a recess in the member,- alocking element movably mounted on the cylinderfoi: engagement with the recess to lock-the piston'men'rber and cylinder together, and for withdrawal from looking position, pressuresresponsive means including "'a movable wall connectedto the locking'eler'nent', passage meansbetwe'e'n the opposite sides of the piston member and the movable wall to conduct fluid pressure from the cylinder to the movable wall to move it and withdraw the locking element from the piston member, and springing meansactin to urge the lockin element into locking position, said passage means comprising opposite passages in the cylinder walls from the wall and connecting into opposite ends of the cylinder, check valve means in each passage to retain pressure conditions produced upon said wall.

3. In combination, a cylinder, a piston oppositely movable therein, bypass means from one side of the piston to the other, resistingly yieldable valve means controlling the bypass, and closing the same until a predetermined pressure difierential exists on opposite sides of the piston, a lockin mechanism including a movable ys resynchronize, because they never'reversef asserts pressure operated wall'and a locking element connected therewith rcr movement into and out of lockin interengageineiit between the piston and cylinder, opposite assage means in the cylinder from the movable wall to the opposite ends of the cylinder, the piston opening one passage at each end of its movement in the cylinder, whereby pressure conditions developed in the ends of the cylinder may be transmitted to the wall to operate the locking mechanism.

4. In a mechanism of the kind described, a

main cylinder, a piston reciprocable therein, mechanism operated by the piston including a powertake-ofi between the ends of the piston, means to admit fluid under pressure to opposite ends of the piston, a groove on the surface of the piston between the ends thereof to provide a channel communicating with the power takeoff, pressure relief means comprising a port in the cylinder communicating with said channel, yieldable relief valve means adapted to control flow through the port, said groove being shaped to establish communication with the port in any position of the piston in the cylinder, and a lockin means, said locking means comprising a second cylinder and a plunger therein, detent depressions in the piston engageable by the plunger, means urging the plunger toward said detents, said port communicatingwith the'secnd cylinder to dispose fluid passing through said relief valve means against the plunger to withdraw it from the detent depressions, and means admitting fluid from the ends of the main cylinder to said port at the the piston. 7

51A double-acting piston motor adapted for continuous reciprocating movements comprising: a cylinder and a piston movable :back and forth therein with fluid pressure chambers at its opposite ends and designated forward and reverse pressure chambers, one chamber being connectible to receive fluid under high pressure while the other receives fluid under low pressure, and vice versa; fluid pressure operated locking means to lock the piston against movement, and means to release the look when high pressure fluid is delivered to either pressure chamber, the locking means including a locking element interengaging the piston and cylinder and a moving member connected therewith that is movable by fluid pressure; connected from 'each'pressure chamber to the .moving member to admit high pressure fluid to the moving member whereby it may release the llocking element each time high pressure is applied to either pressure chamber, and checking valve means controlling each passage means to prevent escape of such high pressure during the end of each stroke of passage means 3 operating intervals to the pressure chamberna'v ing low pressure therein. I

6. The combination of claim 5, wherein there is means to provide escape of fluid fromgthe moving member when the fluid pressure to the pressure chambers is out off, and means normally urging the locking element into locking position. I

7. The combination of claim 5, wherein the passage means connect into the respective pressure chambers at points that establish communication only after the respective pressure strokes of the piston have become started by at least some piston displacement; bypass means from one side of the piston to the other to establish communication between the two pressure chambers; pressure responsive.valve means controlling flow through the bypass means and connected to receive pressures in the pressure chambers, including means yieldable only to pressures higher than the normal piston-operating pres:

' sures to open the valve means and permit high pressure fluid from one pressure chamber to pass to the other and release the locking element.

8. The combination of claim 5 wherein the locking element is interengageable to lock the piston and cylinder at iboth ends of the stroke of the piston.

' 9. A piston motor having a cylinder and a piston, a-lock for interlocking the piston and cylinder, a fluid pressure-responsive member for releasing the lock, passage means connecting the fluid pressure-responsive member and the cylinder to deliver high pressure fluid to the member to cause it to release the lock, check valve means in the passage means to withhold escape of the pressure fluid back into the cylinder when pressure therein is relieved; means to permit escape of fluid pressure from the pressure-responsive member, and resilient means urgin the look into locking position.

HOWARD E. ROSE.

v REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

